Rapid weight loss can be quick and easy -- if you believe the advertising claims.

Fad diets and weight loss supplements promise a slimmer body in no time. In the U.S. alone, consumers spend $33 billion each year on weight loss products.

Do any of these products really produce rapid weight loss? Are they safe? And what are the risks of such fast weight loss? WebMD took a look at some rapid weight loss claims, as well as the available evidence.

Rapid Weight Loss: What Is It?

So many marketers promise "fast weight loss" it's difficult to sort through them all.

Most rapid weight loss pitches fall into these categories:

Starvation Diets

Beyonce popularized the so-called "master cleanse" diet: water, lemon juice, maple syrup, and cayenne pepper. Variations of these diets have been around since at least the 1950s. They often also promise "detoxification" through colonics or enemas.

Diet Pills and Supplements

Dozens of diet supplements promise to speed weight loss. Generally, they claim either to block absorption of nutrients, increase metabolism, or burn fat.

Very Low-Calorie Diets (VLCDs)

One proven method of rapid weight loss is the medically supervised very low-calorie diet (VLCD). Most of what is known about rapid weight loss comes from studies of people on these diets.

Creams, Devices, and Magic Voodoo Spells

There seems to be no end to the dubious ideas promoted in the name of rapid weight loss. Most promise to replace diet or exercise.

Does Rapid Weight Loss Work?

The U.S. Food and Drug Administration (FDA) does regulate dietary supplements; however, it treats them like foods rather than medications.

The FDA also does not regulate claims made by over-the-counter weight loss products. Unlike drug manufacturers, the makers of supplements don’t have to show their products are safe or effective before selling them on the market. This means that dietary supplements do not need approval from FDA before they are marketed.

Aside from the very low-calorie diet and weight loss surgery, no other product, pill, or diet has been proven to work for fast weight loss. The prescription drug orlistat can help, but it works slowly and only with diet and exercise. Orlistat is marketed as Xenical and Alli. Labeling for orlistat notes that it can cause severe liver damage.

In any rapid weight loss program, what really burns fat is not a pill or type of food. It's the drastic reduction of calories, combined with exercise.